This invention concerns a device for the insertion of weft threads into the shed of air looms and also adjustable nozzles which can be used with this device.
It is already known that the variable parameters involved in the insertion of weft threads into sheds of air looms can be adjusted in accordance with measurements carried out on the weft threads during their insertion into the shed. The variable insertion parameters which are usually applied are the working time and/or the working pressures and/or the air flow rate of the nozzles of the loom.
It is already known that, for looms in which several thread types are used, for instance multicolor machines, the aforesaid insertion parameters can be modified according to the weaving pattern. In other words, well known characteristics of the thread type are applied in modifying the variable insertion parameters.
The Japanese Published patent application No. 59-125941 described a method whereby the flow-through aperture of the main insertion nozzle is automatically adjusted according to various weaving parameters and weaving results. However, this method has the disadvantage that it is practically impossible to apply to main nozzles which move with the sley because the nozzles rapidly reciprocate so that a fine and accurate regulation of the aperture is impossible.
It is already known in multicolor weaving to supply the weft threads to a main nozzle by means of corresponding auxiliary nozzles. To this end the weft insertion parameters must be adapted in accordance with the characteristics of the various kinds of weft thread and in accordance with the measurements carried out in the shed whereby a combination of main and auxiliary nozzles can be provided with regulation of the main nozzle by means of a regulating system as described in the above Pat. No. JP 59-125941. This combination is also disadvantageous, however, because a flow-through aperture of the main nozzle must be instantaneously adjusted, sometimes involving a relatively large modification for each color and in many cases also for each shot, which is hardly feasible at very high speeds.